C++ "No overloaded function takes 0 arguments"错误

Question

我有一个正在保存用户名的程序，它的读取用户名功能一直给出这个错误:

Severity Code Description Project File Line Suppression State Error C2661 'std::basic_ifstream>::open': no overloaded function takes 0 arguments ConsoleApplication3 c:\users\main\documents\visual studio 2015\projects\consoleapplication3\consoleapplication3\consoleapplication3.cpp 25

我是 C++ 的新手，不明白这个错误是什么意思，但我有我的代码。

string name2()
{
    string name2;
    ifstream myfile("Userlog.txt");
    myfile.open();
    myfile >> name2;
    myfile.close();
    return name2;
}

Answer 1

string name2;
ifstream myfile("Userlog.txt"); // here you are calling open
myfile.open(); // no version of ifstream. so open what??!!!

上面这行可以翻译成:

ifstream myfile;
myfile.open("Userlog.txt");
myfile >> name2;
myfile.close();